Fans on when ignition in accessory position

[LGAFF]

I have an issue with the fans turning on once the ignition switch is turned into the accessory position, as in supplying power, but the car is not running. I have reset the prom multiple times and even replaced the prom. disconnected the temp switch on the inj housing, and even trying jumpering the AC high pressure line switch

Thoughts, I think the only other potential issue is ECM?

[BigJohn]

Is the engine warm?

[LGAFF]

No this is from the moment you turn on the switch, even when dead cold

[LGAFF]

I should probably mention its only the primary fan... and I did swap relays with same result

[Corvette95]

Check if your A/C pressure switch is unplugged or bad. (on high side line with red upper body)

[LGAFF]

Check if your A/C pressure switch is unplugged or bad. (on high side line with red upper body)


I jumpered the connector ..... didnt change anything, also does the car have to be running to turn it on due to the pressure switch.... this happens on mine in accessory mode

[XfireZ51]

So Lee, with ignition ON but not running, do fans come on?

[LGAFF]

Yes engine is off and fan 1 cones on not both


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[Corvette95]

I jumpered the connector ..... didnt change anything, also does the car have to be running to turn it on due to the pressure switch.... this happens on mine in accessory mode
If the connector is bad or unplugged the fans will run all the time. I am not sure if jumping it will work or if it is a resistance number it is looking for.

[XfireZ51]

Yes engine is off and fan 1 cones on not both


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Is this a new calibration u put in, or has the prom always been there and now this is happening? Does SES flash once on initial ignition ON?

[Corvette95]

Didn't see the part where you asked if the a/c has to be in run for the pressure switch to run the fan....yes.

[LGAFF]

this is a stock 92 prom. Yes Tech one flashes 12, car runs, etc

[Corvette95]

Other than sticking relay, I think they have power from fusible links at all times even with key off, an aftermarket fan switch, or a fault in ignition switch. Has any wiring work been done under the drivers dash such as Vats bypass, alarm, remote door fob etc?

[LGAFF]

Nope all stock wiring... and its only fan 1

[Macroblock]

I'm thinking the primary cooling fan is "controlled by the ECM" thru the Green Connector "C6". This provides a (-) signal to th Primary Fan Relay.

If you disconnect the Green Connector and turn the key to "ON", you can verify if the fan is being activated by the ECM or something else. If it runs with the Green Connector removed, it's not the ECM.

[LGAFF]

I unplugged red and it stopped. Will check green too


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[LGAFF]

I am able to command the fan off with a Tech 1, which I thought was odd...

[Macroblock]

I am able to command the fan off with a Tech 1, which I thought was odd...

That's a good sign. It suggests to me the ECM is capable of controlling its (-) output to the primary fan relay on circuit 409, pin 6 of Green Connector (C6).

Could it be you have a Code 14, 15, 52 or 62 set?

If you have any scan-tool (or any device) connected to the ALDL the fan or fans might come on.

If you have a faulty Heater/ AC Controller.

One or several of these inputs to the ECM could be providing false information causing the ECM to activate the primary fan relay:

AC Request (C2),
AC Fan Request (C8),
Coolant Temp. Sensor (B9),
Engine Oil Temp Sensor (B18),